Have about 1500 miles on the "new" B210 coupe. The mileage course I'm running is 126 mile round trip measured on state highway markers; the speedo reads 132 miles for same distance.
Elevation change is 1700 vertical feet. I drove on no-wind days with air temp between 70-80 degrees F. The first run (in June of this year)I drove 63 mile per hour and averaged 46 mile per US gallon, the second run (today) I slowed down to 57 mph and averaged 49 mile per US gallon. For fuel economy calculations the distance driven was state highway markers.
I drove VERY carefully, gently speeding up or slowing down.
Trany and rear axle are 1976 stock parts that came with the car. Ignition is stock point type, no change to advance curve.
Engine is A12 with compression increased to 10:1 by decking block and milling head. Stock US type pistons with center recess are being used. Wish I had true flat top pistons. Cylinder head is round port MPG type head. I blocked off the water ports to intake manifold, using a 1972 A12 intake manifold. Intake manifold and cylinder head runners are roughened to 60 grit finish using sanding rolls. Intake and exhaust port runners had sharp edges removed, short turns were widened 0.05 inch each side of port for total of 0.10 width increase to help flow turn sharp short turn corners. Exhuast ports were polished. Also enlarged int/exh bowls below valve seats. All valves were back cut with 30 degree angle cut about 0.05 width. Carb is stock A12 small venturis with 1973 OEM jetting. Stock air cleaner, Datsun air filter, and A14 exhaust manifold with stock exhaust system.
The engine was running a little on the warm side, so I installed the larger A/C type radiator, but have not found a shroud to fit. May have to scratch build one.
I'm rebuilding a 1980 Datsun electronic ignition that I'll install this winter. So far so good.

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nice looking engine bay dude.. nice and clean by the pics.

The most important factor is gearing. The stock A14 with 5-speed got 50 mpg. Which transmission, diff gearing and tire size are you running?

Trany is stock 4 speed for 1976 A14. Has the taller first gear ratio. Rear axle is also stock 1976, my FSM says ratio is 3.889:1.
Tire size is 175-70 R13, with 21.5 inch diameter measured from pavement to top of tire. I have a 5 speed trany, but with the heavy car, the engine seems to be doing plenty just to pull the car around.
Just last week bought a 1979 210 with an unbelievable body, I'm talking no rust anywhere. Found it on the high-line northern border of Montana, estate sale, car has sat in a barn full of tractors since 2002. I'll be rebuilding the A14 and installing the 5 speed in the 210. Found a NEW in the box A14 carb with jetting for A14 federal/Canada on ebay a couple weeks ago.

Great to hear about your b210 and it's fuel mileage femtnmax [what's you first name?] I will be following your progess and look forward to the details and changes. Have you ever weighed the B210?

Can you post a few pics of your B310? Sounds like a really nice one!

Cheers,

Mike

femtnmax,

How's your fuel mileage project coming? Any news on the 210?

Mike